Traitor (Captain Scarlet) - Plot

Plot

The Mysterons announce that there is a traitor in Spectrum. In light of a number of unexplained Spectrum Hovercraft crashes in the Australian Outback, Captains Scarlet and Blue are dispatched by Colonel White to investigate Koala Base, where White believes that the vehicles are being sabotaged by a double agent. Scarlet and Blue arrive ostensibly to deliver a series of lectures to the cadets. One cadet, Machin, is suspected by his patrol partner, Johnson, and the commander, Major Stone, to be the double agent, but Machin questions Scarlet's loyalty to Spectrum after Blue describes how the officer was under the control of the Mysterons when the Martians in the attempted assassination of the World President. A fire in Scarlet and Blue's room, apparently deliberate, seems to leave Machin's guilt even more obvious.

The next day, while Scarlet and Blue are accompanying Johnson and Machin in a hovercraft, the vehicle again goes out of control. Machin declares Scarlet the traitor and briefly threatens him, but is disarmed when a jolt throws his gun out of his hand. All four men, including Scarlet with the hovercraft control unit, jump to safety before the vehicle crashes and explodes. From the unit, it is discovered that a valve in the hovercraft's mechanics caused all the accidents. Although presumably being placed by the Mysterons, in a figurative sense it was the "traitor" within Spectrum.